Method of manufacturing electrical connection plug for a multipolar lead of an active implantable medical device

ABSTRACT

A method for constructing a plug for an electrical connection to a multipolar lead for an active implantable medical device includes providing a plug body having an insulating monobloc central core, the monobloc central core having a generally cylindrical shape, a cylindrical side surface, and a housing, providing a connection wire and a conductive pod, attaching the connection wire to the conductive pod, placing the conductive pod into the housing with connection wire extending therefrom, placing a conductive cylindrical ring on the cylindrical side surface, wherein the cylindrical side surface centers the conductive cylindrical ring coaxially about the monobloc central core, attaching the conductive pod to the cylindrical ring to create an electrical contact zone on a cylindrical outer surface of the plug body.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of application Ser. No. 13/423,030filed Mar. 16, 2012, hereby incorporated by reference in its entirety,which claims the benefit of French Application No. 1152166 entitled“Electrical Connection Plug For A Multipolar Lead Of Active ImplantableMedical Device” and filed Mar. 16, 2011, which is hereby incorporated byreference in its entirety.

FIELD

The present invention relates to active implantable medical devices asdefined by the Jun. 20, 1990 directive 90/395/CEE of the EuropeanCommunity Council, more particularly to devices that continuouslymonitor the cardiac activity of a patient and deliver if necessary tothe heart electrical pulses for stimulation, cardiac resynchronization,cardioversion and/or defibrillation in case of a rhythm disorderdetected by the device, and to neurological devices, cochlear implants,drug pumps, and implanted biological sensors. The present invention evenmore particularly relates to an electrical multi-polar connection plugfor a lead such as a monobody lead equipped with both stimulation anddefibrillation shock electrodes.

BACKGROUND

Active implantable medical devices generally include a housing, which isoften called “the generator”, that is mechanically and electricallyconnected to one or more “leads” that have electrodes that in turn comeinto contact with the tissues to which it is desirable to applyelectrical pulses and/or to collect an electrical signal of thepatient's myocardium, nerve, or muscle.

Standardized connection systems have been used for years to ensure aninterchangeability of the leads and generators produced by differentmanufacturers. Thus, the standards called “IS-1” and “IS-4” define anumber of dimensional and electrical characteristics for the leads to beconnected to the generator. For defibrillation or cardioversion leads,wherein electrical stresses are more severe in view of the high energypassing from the generator to the lead, the “DF-1” and “DF-4” standardsdefine the dimensional and electrical characteristics of the connectionsystem.

The complexity of multi-polar leads, which already incorporate specificconstraints in terms of the electrical energy associated with deliveryof pacing or shock pulses, is enhanced by the development of multisitedevices and intracardiac sensors, such as peak endocardial acceleration(PEA) sensors. This complexity leads, in terms of connectivity, to aproliferation of connection plugs, in addition to different standardsdepending on the plugs.

It is thus desirable to obtain a single plug that is subject to a singlestandard having a plurality of electrical contacts to simultaneouslyensure connections to various terminals of the generator for allapplicable energy levels, whether for the collection of depolarizationsignals, for the application of stimulation pulses or for the deliveryof a defibrillation shock. In this context, a single “isodiametric”connection plug, namely a plug having a uniform cylindrical shape,designed to be inserted in a counterpart cavity of the generator, isknown.

EP 1641084 A1 and its counterpart U.S. Pat. No. 7,175,478 (both assignedto Sorin CRM S.A.S. previously known as ELA Medical) describes one suchisodiametric connection plug with the outer cylindrical surface having astack of annular electrical contact zones, realized with alternatingconductive cylindrical rings and insulating zones, the latter designedto electrically isolate the conductive rings. In addition, eachelectrical contact in the cavity of the generator must be isolated fromthe other contacts and from the environment outside the cavity bysuitable seals. Originally placed on the lead, these joints are nowplaced in the cavity because of the fact, more particularly fordefibrillation leads, high voltages are applied to the contact elements.It is therefore essential that the connecting pins of the multipolarleads are dimensionally stable over time and comply, with precisetolerances, with the geometric description of the imposed standards.These requirements help ensure that the electrical contact zones andinsulating zones coincide with the corresponding zones of the cavitiesof the generators, when inserting the connector plugs into the cavities,as well as during the useful life of the active implantable medicaldevice.

In this context, two key parameters must be taken into account, namely,on the one hand, the surface state of the electrical contact andinsulating zones, and on the other hand, the coaxiality of theelectrical contact and insulating zones along the connection plug. Theseparameters are indeed crucial for the quality of the electrical contactin the generator cavity and for sealing the system.

With these constraints, the difficulty of making a plug connector with aconstant diameter along the entire length of the part and with multipleelectrical contacts is increased, which in turn raises manymanufacturing problems. In addition, the constraint of a small outerdiameter (e.g., 3.2 mm according to ISO 27186) limits the designpossibilities, so that the impact of complying with tight tolerancesthat are needed for industrial production can be considerable in termsof time and cost.

In this context, the connection plug described in EP 1641084 A1 and U.S.Pat. No. 7,175,478 mentioned above is not entirely satisfactory, becauseit does not guarantee a perfect coaxiality of the different zones.Indeed, in this prior art plug, the electrical contact zones andinsulating zones are defined by cylindrical elementary parts the axialand angular alignment of which is obtained by longitudinal rods fittedin bores formed in each counterpart section of elementary parts.However, the minimum functional space between the pins and bores toallow stacking of the elementary parts leads to a lack of concentricityof the assembly, detrimental to the electrical contact and sealing ofthe connection plug inside the generator cavity.

U.S. Patent Publication No. 2005/221671 A1 proposes a plug forelectrical connection of a multipolar lead for an active implantablemedical device, said plug having a cylindrical outer surface including aplurality of annular electrical contact zones axially distributed andformed of conductive cylindrical rings, the electrical contact zonesbeing alternately separated by a plurality of intercalary insulatingcylindrical zones. The plug connector further includes an insulatingmonobloc core, a piece having a generally cylindrical shape and aplurality of coaxial centering side cylindrical surfaces, with aconductive ring being placed on at least one centering side surface. Thedesired coaxiality of the conductive rings directly results from thecentering side surfaces formed during the manufacture of the monobloccore piece. The fact that there is a unique piece for the central core,so with no functional clearance, ensures the long term stability of thecoaxial rings.

However, the described structure requires welding the wire “blind” in athrough-hole of the conductive ring, without the possibility of anyvisual inspection of the weld integrity. The problem of correctpositioning of the different rings (i.e., the conductive rings providedwith their welded wire and the insulating rings) during the assembly ofthe plug also remains, while satisfying the constraints of longitudinalalignment and of centering of the rings (namely, for an optimum, anddesired perfect, coaxiality of the electrical contact and insulatingzones), with a sufficient reproducibility and reliability, withoutsignificant increase in production costs and with simple parts andsimple manufacturing and control processes, as appropriate for anindustrial solution with profitability and efficiency for production inlarge quantities.

OBJECT AND SUMMARY

To this end, broadly, the present invention is directed to a multipolarlead having a core comprising a plurality of housings receiving acorresponding plurality of intermediary conductive pods on whichconnection wires are welded, the pods being welded to respectiveconductive rings.

Advantageously, the intermediate pods have a slot for insertion of theconnection wire, aligned in the axis of the core or transverse to thecore axis.

In practice, the conductive rings are brought into position on therespective electrical contact zones by sliding each along the centralcore. To facilitate this operation, the present invention discloses thatthe side surfaces preferably have a centering longitudinal positioningshoulder for the conductive rings. The shoulders of the side surfacesoperate in this way as an abutment for the conductive rings. This inturn provides very good precision in the positioning of the rings.

In one embodiment, to facilitate the introduction of the rings on thecore, advantageously the central core has a longitudinal flat for anintroduction of the conductive rings on the centering side surfaces byreversible elastic deformation. A slightly oval shape is given to therings for introduction into the core, by a slight pressure applied tothe rings, possibly passing over the positioning shoulders, and axiallysliding them into position, then releasing the pressure so that therings recover their initial annular shape and engage and conform closelyto the centering side surfaces.

Preferably, the intermediate insulating areas are formed by insulatingrings. In this embodiment, the insulating rings are alternately threadedonto the core with the conductive rings. In an alternative embodiment,the insulating rings can be made by overmolding on a conductive ring. Inyet another embodiment, the intermediate insulating zones are preferablymade by injection molding of an insulating material. This processconcerns filling the spaces created between the conductive rings to makean isodiametric part that especially satisfies the applicable standard,in this embodiment the ISO 27186 requirements.

According to a preferred embodiment, the core is molded of an insulatingmaterial such as polyetheretherketone (PEEK) or Tecothane (registeredtrademark), which materials are commercially available for medicalpurposes.

Preferably, the cylindrical shape of the core allows a “natural”release, along the axis of opening of the mold, without drawers orspacers. This molding process allows for providing very precisedimensional characteristics on its surfaces, including the centeringsurfaces and on concentricity. Of course, the same mold can be used tomake many parts. This results in excellent reproducibility of thedimensions from one part to another and commercial practicability.

It should be understood, however, that the advantage of the preferredmethod involving molding does not prevent the core from beingmanufactured by machining or any other method of producing the isolatingparts as would be understood by one of ordinary skill in the art.

Advantageously, the present invention also addresses and resolves anissue which pertains to holding the wires in position for the bonding,which wires extend axially along the central core, from the lead to theelectrical contacts of the connection plugs with the generator. In thisregards, floating wires can touch each other or touch a conductive ringand are undesirable.

To this end, the present invention preferably provides means formaintaining conductor connection wires along the cylindrical core whichare formed on the centering side surfaces to avoid this concern. Inparticular, the holding means comprises a longitudinal slot formed onthe centering side surfaces for applying a connection wire against thecylindrical core. Advantageously, the holding means further comprises atleast one second centering side surface intended to hold a connectionwire in at least one longitudinal notch.

Thus, the centering side surfaces have a dual function, that of ensuringthe proper centering of the conductive rings and that of holding inplace the wire for the connection bonding.

DRAWINGS

Further features, characteristics and advantages of the presentinvention will become apparent to a person of ordinary skill in the artfrom the following detailed description of preferred embodiments of thepresent invention, made with reference to the drawings annexed, in whichlike reference characters refer to like elements and in which:

FIG. 1 is a perspective view of a multipolar lead equipped with aconnection plug in accordance with a preferred embodiment of the presentinvention;

FIG. 2 is a longitudinal section of the lead of FIG. 1;

FIG. 3 is a perspective view of the central core of the connection plugshown in FIGS. 1 and 2;

FIG. 4 is a detail view of the core of FIG. 3;

FIG. 5 is a front view of the central core of the FIG. 3 disposed on asupport;

FIG. 6 is a perspective view of one embodiment of the central core ofFIG. 3;

FIG. 7 is a front view of an embodiment of the the central core of FIG.3 having a longitudinal flat;

FIGS. 8 a and 8 b are perspective views of a first method for mounting aconnection wire on an intermediary pod;

FIGS. 9 a and 9 b are perspective views of a second method for mountinga connection wire on an intermediary pod;

FIG. 10 is a top view of the central core of FIG. 3 with intermediarypods;

FIG. 11 is a perspective view of the central core of the FIG. 10 showingmeans for holding the connection wires;

FIG. 12 is a sectional view taken along line AA of FIG. 10;

FIG. 13 is a perspective view of a connection plug in accordance with anembodiment of the present invention during assembly of the conductiverings;

FIG. 14 is a sectional view of FIG. 12 of the connection plug shown inFIG. 13;

FIG. 15 is a perspective view of a connection plug plug in accordancewith an embodiment of the present invention after assembly of conductiverings;

FIG. 16 is a perspective view of the connection plug after anovermolding of the intermediary insulating zones in accordance with oneembodiment of the present invention;

FIG. 17 is a sectional view of the plug of FIG. 16 through a contactzone;

FIG. 18 is a sectional view of the plug of FIG. 16 through anintermediary insulating zone;

FIG. 19 is a perspective view illustrating an embodiment of theintermediary insulating zones;

FIG. 20 is a perspective view illustrating another embodiment of theintermediary insulating zones; and

FIG. 21 is a sectional view of the central core of FIG. 7 showing amethod for introduction of the conductive rings by elastic deformation.

DETAILED DESCRIPTION

With reference to FIGS. 1 and 2, the proximal end of a multipolar leadof an implantable medical device, such as a pacemaker, defibrillator ora resynchronizer, is shown. The lead 1 includes a lead body 20 on whichvarious connection conductors extending through a connection plug 10 arearranged in between an electrical pulse generator (not shown) and thepoles of the lead 1 placed at the distal end of body 20. In theembodiment illustrated in FIGS. 1 and 2, four connection conductors arerepresented, including a hollow conductor 24, such as a coiled cable,electrically connected to an axial pin 104 providing an electricalcontact with the axial generator and having at its center a lumencommunicating with a corresponding lumen 14 formed in the axial pin 104.This allows the introduction of a stylet for the practitioner to guidethe lead during implantation in the patient or for the passage of a(conventional) screw fixation system for the lead.

The hollow conductor 24 is housed inside a flexible sheath 30 ofinsulating material such as silicone, which has excellent fatigueresistance properties. However, to facilitate its introduction into thevenous system, the sheath 30 is externally provided with a coatingmaterial having a low friction coefficient, for example, polyurethane.

In addition to the hollow conductor 24, the sheath 30 includes, in thenon-limiting example illustrated in FIG. 2, three other connectionconductors, the wires 21, 22, 23 whose proximal ends are respectivelyconnected to three zones 11, 12, 13 of ring electrical contact axiallylocated along the connection pin 10. As can be seen in FIGS. 1 and 2,the latter is a multipolar cylindrical connection pin, plugged in asingle movement in a counterpart cavity of the generator. This method ofsimultaneous plugging ensures the electrical connection of the variouselectrodes located at the poles of the lead 1 to the correspondingterminals of the generator. Such a multipolar connection plug is notablydescribed in EP 1641084 A1 and U.S. Pat. No. 7,174,478 mentioned above.

The plug 10 of FIGS. 1 and 2 forms an “isodiametric” assembly, that isto say in which the zones 11, 12, 13 of annular electrical contact andthe intercalary isolating zones 31, 32, 33, 34 alternately separatingthe contact zones exhibit a smooth cylindrical outer surface. In theembodiment illustrated in FIGS. 1 and 2, the zones 11, 12, 13, are madeby conductive cylindrical rings 101, 102, 103 which are connected to thewires 21, 22, 23 according to a method described hereafter.

The connection plug 10 is organized around a generally cylindricalhollow monobloc central core 200, an exemplary embodiment of which isshown in FIG. 3. As indicated above, core 200 can advantageously be madeby natural molding of an insulating material such as PEEK(polyetheretherketone) or Tecothane (registered trademark). Recessesgenerically denoted 270 in FIG. 3 are provided on the body of the core200 to provide a form that is useful to simplify the removal of secondretaining side surfaces 262 a (see FIGS. 4, 11).

The central core 200 is mainly characterized by the presence of sidesurfaces 211 a, 211 b, 212 a, 212 b, 213 a, 213 b for coaxial centering,to obtain a very simple and low cost optimum coaxiality of the annularconductive rings 101, 102, 103 when during the assembly of the plug 10,they are placed on the side surfaces. To this end, the curvature of theside surfaces and the inner curvature of the rings must be identical.FIG. 4 is a more detailed view of the side surfaces 213 a, 213 b.

The electrical connection between the connection wires 21, 22, 23 andthe annular conductive rings 101, 102, 103 preferably can be performedas follows. Initially, according to FIGS. 8 a, 8 b, 9 a, 9 b, theconnection wires 21, 22, 23 are connected to intermediate conductiveterminals pods, generically referenced 240, which are disposed withinhousings 201, 202, 203 provided on the core 200 and which can be seen ingreater detail in FIGS. 3, 4, 6, 10.

Pods 240 are preferably made of a biocompatible conductive material,such as stainless steel 316 SS or MP35N. The connection wires 21, 22, 23are preferably protected by an insulating sheath made of EthyleneTetraFluoroEthylene (ETFE) or PolyTetraTluoroEthylene (PTFE), the wiresbeing then stripped to their end connected to the terminal throughintermediary pod 240. Pods 240 can be machined.

Given the position of housings 201, 202, 203 on core 200, that is to sayat the location of annular rings 101, 102, 103, the external curvatureof pod 240 must be compatible with the inner curvature of the rings.

Two embodiments of pod 240 are proposed. The first version, asillustrated in FIGS. 8 a, 8 b, allows directly alignment of connectionwire 23 in the axis of core 200. In this case, to allow easierintroduction of connection wire 23, intermediary pod 240 has aninsertion groove 241. In the second version, as illustrated in FIGS. 9a, 9 b, wires 21, 22 are transversely placed, making it necessary tobend them and fold them to realign them in the axis of core 200 andredirect them to body 20 of the lead.

The electrical connection between connection wires 21, 22, 23 points andintermediary pod 240 can be achieved by laser welding, electric weldingor any other suitable technology for linking together two metal parts.

Then, pods 240 provided with their respective wires are placed inhousings 201, 202, 203. The wires 21, 22 which are transversely comingout of the axis of the core 200 are inserted into slots formed on theside surfaces 212 a and 211 b and then they are bent and folded so thatthey extend along the core 200, in parallel to its axis, as shown inFIG. 11.

The assembly operation can be performed under conventional binocularviewing, with the support tooling shown in FIG. 5, wherein the core 200is placed on a horizontal support on a hollowed plate 2 with two lateralwings 230 a, 230 b arranged at the end to the core.

According to an advantageous feature, core 200 is provided with meansfor maintaining connection points of wires 21, 22 in their positionillustrated in FIG. 11, namely against the core and parallel to itsaxis. These holding means generally include longitudinal notches formedon the centering side surfaces.

For example, the section view of FIG. 12 shows longitudinal slots 253 a,253 b formed in the centering side surfaces 213 a, 213 b, these notchesbeing intended to respectively apply and maintain the connection wires21, 22 against the core 200. As shown in FIG. 11, connection wire 22 isalso maintained by longitudinal slot 252 a of side surface 212 a.

In order to improve the retention position of the connection wires,second centering side surfaces are provided on the core 200 to retainthe connection wires 21, 22 in the longitudinal slots once they areintroduced there. As illustrated in FIG. 11, for example, the secondretaining side surfaces of wire 22 are referenced 261 a, 262 a. Otherside surfaces of this type, not shown in the drawings, are symmetricallypresent to hold the wire 21 into the corresponding slots.

According to FIG. 13, conductive annular rings 101, 102, 103 are thenput in place by sliding along the axis of core 200 to get themrespectively next to pods 240 to which they must be electricallyconnected. FIG. 14 shows a sectional view of the final disposition ofthe conductive ring 103 around the core 200. The core 200 equipped withall conductive rings is shown in FIG. 15.

Rings 101, 102, 103 are then welded to intermediate pods 240 by laserwelding, electrical welding or any other suitable technology. This canbe done ring after ring or on all the three rings placed at once on apositioning tool. It should be understood that the welded connectionshould not affect the surface finish and cylindricity of the rings. Forthis, for example, a welding on the side of the ring, tilting theassembly formed by the core 200, conductor wires 21, 22, 23 connected topods 240 and to rings 101, 102, 103 can be performed. This welding stepis preferably a perfectly controlled and inspectable process, madeeasier by central core 200 which partly plays the role of an internaltool.

The conductive rings have an outer diameter given by the applicablestandard, e.g., ISO 27186. Their positioning is critical, as is theircoaxiality. As already mentioned, the coaxiality is achieved bycentering the side surfaces on which the rings are in support. Thelongitudinal positioning can be ensured by shoulders 221 a, 221 b, 222a, 222 b, 223 a, 223 b respectively carried by side surfaces 211 a, 211b, 212 a, 212 b, 213 a, 213 b that can be seen in FIG. 6, and againstwhich rings 101, 102, 102 abut.

In this embodiment, it is expected that core 200 has a longitudinal flat270, shown in FIG. 7, allowing introduction of the conductive rings onthe centering side surfaces by reversible elastic deformation. As shownin FIG. 21, a conductive ring, such as ring 101 may according to thismethod be brought into position by successively crossing shoulders 223a, 223 b, and shoulders 222 a, 222 b.

The final step is to fill the spaces 111, 112, 113, 114 shown in FIG. 2between rings 101, 102, 103 with an insulating material to achieve theintercalary insulating zones 31, 32, 33, 34 alternately separating thecontact zones 11, 12, 13, as shown in FIG. 1. In this operation, it mustbe ensured that the connection plug 10 is fully isodiametric inaccordance with the applicable standard, e.g., ISO 27186, and that itguarantees the tightness of the system, which results, as noted above,in the quality of contact of the plug 10 with the seals arranged in thecavity of the generator receiving the plug.

Filling spaces 111, 112, 113, 114 can be achieved, for example, byovermolding or injection of glue or plastics, or of another insulatingmaterial. FIGS. 17 and 18 respectively show a section of connection plug10 through electrical contact zone 13 and a section through insulatingzone 33 after overmolding with an insulating material 280.

According to an alternative embodiment as illustrated in FIG. 19, theisodiameter desired for plug 10 is obtained by providing a stack ofinsulating rings, such as those referenced 121, 122 in FIG. 20 above,and of conductive rings, the coaxiality of all rings being provided bythe centering side surfaces described above, the connection between aconductive ring and a subassembly formed by a connection wire and thecorresponding pod being performed before each insertion of an insulatingring.

The second variant of FIG. 20 implements pairs consisting of aninsulating ring overmolded onto a conductive ring, such as pairs ring121/ring 101 and ring 122/ring 102, each pair being connected by theconductive ring to a subassembly connection wire/pod before theintroduction of a new pair.

It should be understood by a person of ordinary skill in the art thatthe present invention not only greatly simplifies the assembly of amultipolar lead connection plug, but it also allows a visual inspectionat each stage of assembly. The operator thus has better control at eachstage of the process.

In addition, the connection plug of the present invention can either beperformed directly on an existing lead body or subsequently be connectedto the lead. This allows the possibility to outsource the manufacturingof the plug and to adapt it to any lead body.

One skilled in the art will appreciate that the present invention can bepracticed by other than the embodiments described herein, which areprovided for purposes of illustration and not of limitation.

What is claimed is:
 1. A method for constructing a plug for anelectrical connection to a multipolar lead for an active implantablemedical device, comprising: providing a plug body having an insulatingmonobloc central core, the monobloc central core having a generallycylindrical shape, a cylindrical side surface, and a housing; providinga connection wire and a conductive pod; attaching the connection wire tothe conductive pod; placing the conductive pod into the housing withconnection wire extending therefrom; placing a conductive cylindricalring on the cylindrical side surface, wherein the cylindrical sidesurface centers the conductive cylindrical ring coaxially about themonobloc central core; and attaching the conductive pod to thecylindrical ring to create an electrical contact zone on a cylindricalouter surface of the plug body.
 2. The method of claim 1, whereinproviding the plug body having an insulating monobloc central core, themonobloc central core having a generally cylindrical shape, acylindrical side surface, and a housing includes molding.
 3. The methodof claim 2, wherein the monobloc central core is molded from at leastone of polyetheretherketone and Tecothane.
 4. The method of claim 1,wherein providing the plug body having an insulating monobloc centralcore includes releasing the insulating monobloc central core from a moldwithout drawers or spacers.
 5. The method of claim 1, wherein providingthe plug body having an insulating monobloc central core, the monobloccentral core having a generally cylindrical shape, a cylindrical sidesurface, and a housing includes machining.
 6. The method of claim 1,wherein attaching the connection wire to the conductive pod includes atleast one of laser welding and electric welding.
 7. The method of claim1, wherein attaching the conductive pod to the conductive cylindricalring includes at least one of laser welding and electric welding.
 8. Themethod of claim 7, wherein the monobloc central core aligns theconductive cylindrical ring for welding.
 9. The method of claim 1,wherein placing the conductive cylindrical ring on the cylindrical sidesurface includes reversible elastic deformation of the conductivecylindrical ring.
 10. The method of claim 1, further comprising:providing an intercalary insulating cylindrical zone adjacent to theelectrical contact zone on the cylinder outer surface of the plug body.11. The method of claim 10, wherein providing an intercalary insulatingcylindrical zone includes overmolding the conductive cylindrical ring.12. The method of claim 10, wherein providing an intercalary insulatingcylindrical zone includes alternately threading insulating rings withthe conductive cylindrical rings onto the plug body.
 13. The method ofclaim 10, wherein providing an intercalary insulating cylindrical zoneincludes filling a space created by the conductive ring by injectionmolding with an insulating material.